Milo g



(No Model.)

M. G. KELLOGG. MULTIPLE SWITGHBOARD.

No. 592,425. Patented Oct. 26,1897.

[71116271077 M40 6. laLoc-ie, 6 7m ago rugs UNITED STATES PATENT Fries.

. MILO G. KELLCGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SIVITCIIBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent N 0. 592,425, dated October 26, 1897. Application filed March 9, 1895.. Serial No. 541,161. (No model.)

To all whom zit may concern.-

Be it known that I, MILO G. KELLOGG, a citizen of the United States, residing in the city of Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates especially to a metallie-circuit telephone-exchange system.

It consists in a system of calling, switching, testing, and clearing-out signals which I shall describe and claim in detail.

In the accompanying drawings, Figure 1 illustrates the central-oflice apparatus, and Fig. 2 the subscribefis-station apparatus, of my invention, Fig. 3 shows the line-annunciator which is used in the system, with its main-line and local magnets, and self-restoring and retaining mechanism which is employed in my invention.

In Fig. 1, A and A are two multiple switchboards, to each of which all the lines of the exchange are connected. As many boards or sections may be used as are necessary for the exchange in which the system is used. Each switchboard or section has a switch for each line of the exchange. The line-switches are marked S S. Each switch has two contact pieces (marked gj) with which, respectively, the two contact-pieces of the loop-switch plugs shown in Fig. 1 and marked D D are connected when a plug is placed into the switch for switching. These contact-pieces g j are connected with the main-line circuit, as will hereinafter be described, and may therefore be called the main-line contacts of the switch. Each switch has also three othercontact-pieces (marked a, b, and d) which are insulated from said other contact-pieces and are normally out of contact with each other; but when a switch-plug is inserted into a switch it presses the contact-piece a into contact with Z) and (Z. When the plug is withdrawn, the contact of a with b and d is automatically broken. The contacts a, b, and cl are connected to the local system for disconnecting the annunciators and for testing, as will be described, and may be called the local contacts of the switches. The last-mentioned contact-piece dis at or extends to or near the front of the switch, so that an operators test contact-piece may be readily connected to it for testing.

Z l are the switch-holes adapted to receive the plugs, and r r are the rubber pieces 011 which the metal parts are mounted.

The loop-switch plugs shown in Fig. 1 and adapted to be inserted into the line-switches are of the'shape substantially as shown, and each plug has two contact-pieces, (marked on m.) \Vhen a plug is placed into a switch, its contact m forms connection with the contact 9 of the switch, and its contact on forms connection with the contact j of the switch, while the rubber insulation of the plug presses the piece a of the switch into contact with the pieces I; and d.

The switches and plugs may be of the shape and construction substantially as shown. They may, however, be greatly changed in shape and construction and yet have substantially the same switch parts, operating in substantially the same manner or forming substantially the same connections, as heretofore described.

W WV are the line-annunciators, of which there is one for each line. These annunciators are distributed among the several boards or sections ofthe exchange and each is placed at the section where its subscribers calls are to be answered. The line-annunciators, as shown in Fig. 3, have each a mainline electromagnet (marked it) and a local electromagnet, (marked 0.) The armature p of the main-line eleetromagnet n is pivoted, as shown, and has a lever extending to the front of the annunciator, with a catch which normally holds the shutter or drop q. Then the electromagnet n is energized by callingcurrent passing through its helix, it attracts and moves its armature p, and thereby "releases the catchfrom the shutter or drop pivoted at the bottom, which latter will then fall and indicate a call, unless prevented from doing so by the retaining mechanism, which will now be described.

The armature p of the local electromagnet ois in the rear of the shutter q, is pivoted at its top, and exten ds normally close to the face of the core of its electromagnet. The lower end of the armature is connected by a link with the shutter, just above the fulcrum of the electromagneto is energized by being placed in closed circuit with a battery or other constant source of electricity, its armature p is attracted to the position shown by the solid lines and is retained in that position as long as the electromagnet is thus energized. When the armature p is thus attracted to this position by means of the link connection shown,

it carries the shutter g to its normal position, where it is engaged by the catch of the lever of armature p, and it, moreover, holds or retains the shutter in this normal position so long as the electromagnet 0 may thus be energized, whether or not during this time the electromagnet n may be energized by callingcurrents passing through it. If the circuit of 0 is closed while q is in its normal position, the armature 19 will be held in its normal position, preventing g from falling to indicate a call. Thus the shutter q is restored to its normal position when the magnet 0 is energized and is retained in its normal position and prevented from indicating a call as long as the magnet is thus energized. Each operator has as many pairs of loop-switch plugs D D as she may need in order to properly attendto the lineswhich are alloted to her. v

Y Y are switches,one for each pair of plugs.

Each switch Y has two switch-levers and two pairs of contact-bolts, on which, respectively, the two levers may be alternately placed. It has also another or fifth contact-bolt on which one of the levers may be placed. The switchlevers are adapted to occupy three positions, at the will of the operator, in one of which they are in contact with one pair of said bolts, in another of which they are in contact with the other pair of bolts, and in the third position of which one of them is in contact with said fifth bolt.

ttare the operators telephones, of which there is one for each operator.

:0 a: are retardation-coils, one for each telephone.

B B are calling-generators, of which there 1 ma be one for each 0 erato'r or one "enera- .tor may answer for several or all of the operators.

V Vareclearing-out annunciators, of which there is one for each pair of plugs.

test-circuit, as will be hereinafter described.

into the local annunoiator-circuit, as will hereinafter be described. j

The two contact-pieces m m of a pair of plugs are connected together by a flexible conductor, and the two contact-pieces an m are connected together by another flexible conduct-or. The two flexible conductors of a pair of plugs are connected to the two levers of the switch Y of the pair of plugs. The flexible conductors are long enough so that a switch-plug may be placed in any switch of the section at which it is located. The bolts of one pair of contact-bolts of each switch Y are connected together through the operators telephone. The bolts of the other pair are connected together by a circuit connection,

from the center of which is a connection to one side of the calling generator B. The other side of the generator is connected with ground. The last or fifth contact-bolt of each switch Y is connected to one side of the clearing-out annunoiator o of the pair of plugs, and the other side of the annunoiator o is connected to ground. One side or branch of each metallic-circuit line is connected to one of the main -line contacts-say g-of each switch of the line and the other side or branch is connected to the other main-line contact say jof each switch of the line. The two sides or branches of each line are bridged ciator W of the line.

The local connections of the systems are.

substantially as follows: All of the contacts a a of all the switches of the exchange are connected together to a common circuit con- -nection, and thence through battery 13 to the circuit connection which connects the retardation-coils to the operators telephonep One side of the battery Bis connected to this circuit connection before it passes to the battery B All of the contacts I) b of all of the switches of any given line are connected together and are also connected through the 1 local magnets of the annunciators of the line to the other side of the battery B than that side which is connected to the-contacts a a .of the switches.

The contacts at d of each line are connected together.

The circuit connections, both main-line and local, are shown substantially as above described. For convenience of illustration the main-line circuit and connections are repre jsented by solid lines and the local circuits and connections are represented by broken lines.

The side of each operators telephone which is connected to contactsm m of a pair of plugs, when the switch Y of that pair of g plugs is in position for the telephone to be 5 in circuit with them, is connected with the retardation-coil a: of the telephone, and B is a test-battery connected into the local thence to battery'B", as shown and as above 7 described. B is the annunoiator-battery, connected v In the subscribefls-station apparatus shown in Fig. 2, 1 is the telephone-switch; 2, the subscribers telephone; 3, the subscribers callinggenerator; 4:, his signal-receiving bell, and 5 a resistance-coil of the resistance, which will hereinafter be described.

The calling-generator has the usual automatic device by which its armature is automatically short-eircuited while it is not being operated. It should preferably be an alternate-current generator.

The switch 1 has a lever and three insulated contact-pieces, with two of which the lever is in contact when the telephone is on the switch and with the third of which the lever is in contact when the telephone is off the switch. One of the first-mentioned contacts is connected with the ground. Both sides of the line are connected to the switchlever. In one side are the calling-generator and the signal-receiving bell and in the other side are the subscribers telephone and the rcsistance-coil 5. The circuits to the switchcontacts are substantially as shown and such that when the telephone is on the switch the telephone is short-circuited, and when the telephone is off from the switch the callinggenerator and si gnal-receivin g bell are shortcircuited.

The resistance of one side of the line from the switch-lever to the connection with one side of the line-annunciator should normally (or when the subscribers telephone is not oit from the switch) be substantially the same as the resistance of the other side of the line from the switch-lever to the other side of the line-annunciator. This may be obtained by making the resistance of the coil 5 of the right amount to produce this equality of resistance. Of course the lines themselves may be constructed so as to obtain this equality of resistance. All the annunciators should be constructed so as to offer high retardation to alternating currents of high frequency, such as telephone-currents.

The operation of the system is as follows: \Vhen a subscriber operates his calling-generator, he sends a signal over his metallic circuit, which operates his line-annunciator. The operator who receives the indication then places one of her switch-plugs D into the switch of the line, the levers of the switch Y, to which the plug belongs, being in the position in which the two sides of her telephone are connected to the two levers of the switch. ller telephone is then in complete or closed metallic circuit with the line and she will receive verbally the order of the subscriber. This complete circuit exists because the two contacts of the plugs (which are connected to the two levers of the switch Y) are by their contact with the two contacts 9 j of the switch connected to the two sides, respectively, of the line. This operation of placing the switchplug in the switch of the line closes the local circuit in which is the local magnet of the annunciator. The local magnet is thus energized by the battery B attracting its armature and restoring and retaining the shutter q in its normal position, as heretofore described. lVhen the operator finds out what line is wanted, she tests that line, as will hereinafter be indicated, and if she finds that it is not in use she places the mate of the plug first usedin the switch of the line wanted. This also closes the local-magnet circuit of the annunciator of this line and holds or retains its shutter in its normal position as long as the local circuit is thus closed, or while the plug is in the switch. The operator then moves the levers of the switch Y so that they are in contact with the other pairof bolts, (which are grounded through the generator B.) Current from her generator will then pass from ground at the central office through the two sides or branches of the metallic circuit of the line wanted in split or derived circuit to the ground at the subscribers station. As the two branches of the line are of the same resistance as much current will pass through one branch as the other. The current which passes through the signal-receiving bell of the subscriber wanted will be sufficient to ring his bell. The operator then moves the switch-levers of the switch Y so that one of the levers is on the said fifth contact-bolt connected to ground through the clearing-out annunciator of the pair of plugs. The two lines are thus connected together into a complete metallic circuit for conversation, and one side of the circuit is grounded through the clearing-out annunciator. hen the lines are thus connected, their combined circuit is bridged or cross-connected through the annunciators of both lines. As these ann unciators offer high retardation to telephone and other alternating currents, substantially none of the telephone-current generated during the conversation will pass through them.

WVhen the call is sent by the operator, the subscribers line-annunciators will not be operated, because the resistances from the generator to each side of the line-annunciator are the same, as are also the resistances from each side of the annunciator through the two sides or branches of the line to the subscribers ground, and thus none of the calliug-current will therefore pass through the lineannuneiator. Should for any reason this equality of resistances be destroyed, so that part of the operators calling-current will pass through the line-annunciators, the operation of the retaining mechanism,as hereinafter described, will prevent their being operated.

The clearing-out system is as follows: Each subscribers apparatus is connected into his circuit so that his calling-generator is in the circuit between his ground and the ground connection through a clearing-out annunciator when the line is switched for conversation. The clearing-out signal is sent after the subscriber has placed his telephone on his switch. The current generated will therefore divide into four parts, passing through four branch or derived circuit-s. One of these cir- IIO cuits is from the subscribers ground through his generator and one branch of the line to the clearing-out annunciator'and thence to ground. Two other circuits through which part of the current passes are through his metallic-circuit line at the central office and thence in split circuit through the two lineannunciators. The fourth circuit is by way of the subscribers station of the other line. Ifwhen the clearing-out signal is sent the telephone of the other subscriber is not yet placed on its switch, the circuit is through the metallic-circuit line of the other subscriber. If, however, both subscribers have their telephones on their switches, it is also from the ground at one station through one side of'the combined circuit to ground at the other station. The line-annunciators of the two lines will not then be operated, although part of the current generated for the clearingout signal passes through them, because their shutters are then retained or held in their normal position by their local magnets and mechanism, as heretofore described. The clearing-out annunciator not having retaining mechanism, but being of ordinary construction, will respond to the clearing-out current passing through it. The operator .will then remove the plugs from the switches of the lines. The local annunciator-circuits of the lines being thus automatically opened, each annunciator will thus be free to respond to any calling-current sent through it.

The operation by which the line-annunciators are automatically restored if they indicate a call and are locked or prevented from being operated by a calling-current whenever the line is switched at the central oflice is briefly this Whenever a plug is placed in the switch of a line, it automatically closes the local contacts a b' of the switch, as heretofore described. This brings the battery B and the local magnets o oof the line-annunciators of the line into a closed local circuit, which operates, as heretofore'described, to restore the shutter if it indicates a call and to prevent the annunciators from responding or indicating when calling-currents pass through them. The closed local circuit may be traced thus: from the contact b of the switch, to and through the battery B, and thence through the helix of the electromagnetic device to the contact CL of the switch. When the plug is removed, the contact between a and b is broken and the local circuit is therefore open, thus demagnetizing the local magnets of the annunciators and removing the locking mechanism, so that the annunciators may respond to calling-currents.

The test system is as follows: When an operator desires to test any line to determine whether or not it is switched at the central office, she places the contact m of one of her switch-plugs on the contact-piece d of the switch of the line, the switch Y being then in position so that her telephone bridges across the two cord-circuits of the plug. If the line is then switched for use, a closed circuit is established which contains the battery B and the operators telephone, and the operator will hear a click in her telephone and know that the line is already in use. This closed circuit may be traced as follows: through the retardation-coil and telephone of the operator to the contact m of the plug used in testing thence to the contact d, to which the plug'is' applied, and thence to the contact (1 of the switch at which the line is switched, thenceto contact a of that switch, which is then in contact with d, and thence through the common connection of the contacts a a of the switches of the exchange and the battery B to the retardation-coil. If the line is not switched at any board, no closed circuit will be established on testing, because no contact 61 of the line is in contact with its spring a. The operator will therefore hear no click in her telephone and will thereby know that the line is not in use and will place a plug in its switch. It is evident that the subscribers signal-receiving bell might also be placed in the ground connection at his station. In that case all the calling-current which the operator sends over his line would pass through his bell. the resistances of the two branches of the line .should' in this case also be made substantially alike. Certain features of my invention are also applicable to systems in which the lineannunciators are prevented from being operated when either the operator calls or a clearing-out signal is sent by other instrumentalities than those heretofore indicated. My invention in these respects is broad enough to include these variations.

Other forms of lockin g or retaining annunciators than the one shown and described herein, or other forms of annunciators which both restore the shutter and lock or retain it when the line is switched, may be used for the line-annunciators.

I claim as my invention 1. In a telephone-exchange system, metallic circuit lines, multiple switchboards, switches, one switch for each line on each board, each switch having two contact pieces For the purpose heretofore indicated or terminals to which respectively the two sides or branches of its line are connected, andmeans at each board to connect together any two lines into a metallic circuit for conversation by connecting together their respective contact pieces or terminals at that board, in combination with line-annunciators, one of each line located at a switchboard and permanently bridged across between the two sides or branches of its line, a clearing-out annunciator grounded on one side and connected on its other side to one side of a metallic circuit established by connecting any two lines together for conversation; a callinggenerator at each subscribers station in the closed metallic circuit of its line whenever it is operated to send any signal, (either primary or clearing-out;) means for grounding each closed metallic circuit at the subscribers station while the subscriber sends a clearing-out signal with the ground connection on such side of the generator that the generator and the clearing-out annunciator are in a closed ground-circuit which comprises that side or branch of the line to which the clearing-out annunciator is directly connected, and electromagnetic apparatus for each annunciator, each in its normally open circuit with battery, said circuit being automatically closed by the switching of the line for conversation, and said electromagnetic apparatus of the ann unciator of the line, then or when the line is thus switched, operating to prevent the annunciator from being operated to indicate the passage of calling-current.

2. In a telephone-exchange system, metallic-circuit lines, a switchboard, switches, one switch for each line on said board, each switch having two contact pieces or terminals to which respectively the two sides or branches of its line are connected, and means to connect together any two lines into a metallic circuit for conversation by connecting together their respective contact pieces or terminals, in combination with line-annunciators, one for each line, permanently bridged across between the two sides or branches of its line, a clearing-out annunciator grounded on one side and connected on its other side to one side of a metallic circuit established by connectingjany two lines together for conversation, a calling-generator at each subscribers station in the closed metallic circuit of its line, whenever it is operated to send any signal, (whether primary or clearing -out;) means at each subscribers station for grounding his closed metallic circuit while he sends a clearing-out signal, with the ground connection on such side of the generator that the generator and the clearing-out annunciator are in a closed ground-circuit which comprises that side or branch of the line to which the clearing-out annunciator is directly connected, and electromagnetic apparatus for each annunciator, each in its normally open circuit with battery, said circuit being automatically closed by the switching of the line for conversation, and said electromagnetic apparatus of the annunciator of the line, then or when the line is thus switched, operating to pre vent the annunciator from being operated to indicate the passage of calling-current.

3. In a telephone-exchange system, two metallic-circuit lines temporarily connected together at the central office into a metallic circuit for conversation, and the annunciator of each line, then or when the lines are thus connected, in a bridge at the central office be tween the two sides, in combination with electromagnetic apparatus for each line, including an auxiliary electromagnet in a normally open circuit with battery, but whenever the line is thus switched for conversation, said normally open circuit being closed to actuate said electromagnetic apparatus of the annunciators to prevent them from being operated to indicate the passage of calling-current, a clearing-out annunciator in a circuit connection from said. metallic circuit to ground, a calling-generator at each subscribers station in the closed metallic circuit of the line Whenever operated to send a call, and a ground connection to each line at each subscribers station, when his generator is operated to send a clearing-out signal, with the calling-generator and the clearing-out annunciator between said ground connection and the ground of the annunciator at the central office.

4. An electric annunciator containing a main-line electromagnet and an armature therefor, with a lever and a catch, a pivoted shutter normally inclined to fall by gravity and held by the catch, but released from said catch when said electromagnet is energized by electric current, an auxiliary electromagnet and an armature therefor, and a link connection between said shutter and said armature, said shutter on falling when released from said catch while said auxiliary electromagnet is not energized carrying the armature of the auxiliary electromagnet away from its core and said auxiliary magnetwhen energized by the passage of electric current attracting its armature and through said link connection carrying said shutter to its normal position and retaining it there.

5. An electric annunciator containing a main-line electromagnet, and an armature therefor, with a lever and a catch, a shutter pivoted at its lower end, normally inclined to fall by gravity, and held by the catch, but released from said catch when said electromagnet is energized by electric current, an auxiliary electromagnet and an armature therefor pivoted at its upper end, extending in proximity to the core of the electromagnet and connected at its lower end byalink connection to said shutter, near to and above the pivot of said shutter, said shutter on falling. when released from said catch while said auxiliary electromagnet is not energized carrying the armature of the auxiliary electromagnet away from its core and said auxiliary magnet when energized by the passage of electric current attracting its armature and through said link connection carrying said shutter to its normal position and retaining it there.

6. An electric annunciator containing a main-line electromagnet and an armature therefor, with a lever and a catch, a shutter pivoted at its lower end, normally inclined to fall by gravity, and held by the catch, but released from said catch when said electromagnet is energized by electric current, an auxiliary electromagnet and an armature therefor pivoted at its upper end, extending in proximity to the core of the electromagnet and connected at its lower end by a flexible connection to said shutter, near to and above the pivot of said shutter, said shutter 011 falling when released from said catch while said auxiliary electromagnet is not energized carrying the armature of the auxiliary electromagnet away from its core and said auxiliary magnet when energized by the passage of electric current attracting its armature and through said flexible connection carrying said shutter to its normal position and retain ing it there. IO

In testimony whereof I have hereunto subscribed my name.

MILO G. KELLOGG. Witnesses:

G. M. BROOKE, B. W. MILLER. 

